The present invention relates to such sheet metal working centres in which sheets are handled to machine them to a desired form. As a general rule, the objects to be machined are metal sheets, e.g. 1250×2500 mm or 1500×3000 mm in size. Typically, the thickness of the metal sheets is variable between 0.5 mm and 3.5 mm, wherein reference is generally made to so-called thin sheets, or thin sheet metal working centres, respectively. Typical machinings performed for sheets in a sheet metal working centre include e.g. punching, angular cutting, thread cuffing or riveting. Other operations that can be directed to a sheet include e.g. providing the surface of an otherwise completed sheet with various markings using an adhesive-label machine (EAN coding), or the like.
As to the prior art, reference is made to a U.S. Pat. No. 4,658,682, describing one automatic sheet metal working machine. A sheet metal working machine typically comprises a frame and a carriage arrangement moving relative to the frame and comprising a first carriage and a second carriage that is mounted in the first carriage and moving in a direction perpendicular relative to the direction of motion of said first carriage. Said second carriage comprises mounting means, e.g. a set of mounting jaws, to secure the edge portion of the sheet that is to be machined to the carriage arrangement. The first and the second carriage of the carriage arrangement can be used for moving the sheet to be machined substantially in the coordinates X, Y of the main plane of the sheet relative to the machining unit used, e.g. a punch or a cutter.
Modern machining units intended for sheet metal work are controlled by numerical computer control. In the memory of a control centre situated in connection with the sheet metal working centre, there is stored a machining program, which a machining unit runs automatically under control of the control centre. Programs and devices related to automatic control of machining units intended for sheet metal working as well as functions related thereto, are well known in the field as such, and therefore these will not be described in more detail in this context.
Even though the sheet metal working machine disclosed in U.S. Pat. No. 4,658,682 is advantageous as such, modern demands on sheet metal production have come up with problems in this kind of sheet metal production, in which various machining units are used for machining a sheet to be machined one machining phase at a time. The purpose of the present invention is to disclose an improved method in sheet metal machining, in which a plurality of various machinings or the like are directed to a sheet. By using the basic solution of the invention it is possible to attain a versatile sheet metal working centre that implements a total range of certain machining phases in a single complex. Adapting the basic solution of the invention, a variety of sheet metal working centre complexes are provided, that have a customized number of machining units or the like.